The present invention relates to a novel non-aqueous battery of a thin configuration. More specifically, the present invention is concerned with a non-aqueous battery of a thin configuration, comprising a hermetically sealed pouchy casing enveloping an electrochemical cell, and terminals electrically connected to a cathode and an anode of the electrochemical cell, wherein the pouchy casing comprises opposite sheets of at least-three-layer laminates, each comprising an inner thermoplastic resin layer, a middle metal foil layer and an outer electrically insulating material layer, and the pouchy casing has an elongated, hermetic adhesion area along a periphery of the pouchy casing, in which adhesion area the opposite inner thermoplastic resin layers are melt-adhered to each other, thereby forming a hermetic seal of the pouchy casing, wherein the middle metal foil layer (2) has a peripheral elongated region in said elongated, hermetic adhesion area of the poaching casing, with the terminals extending through and protruding from terminal-withdrawal sites in the elongated, hermetic adhesion area toward the outside of the pouchy casing, and wherein the non-aqueous battery satisfies at least one of the following characteristics (i) and (ii):
(i) the peripheral elongated region of the middle metal foil layer (2) has cut-out portions around the terminal-withdrawal sites in the elongated hermetic adhesion area of the pouchy casing through which the terminals extend wherein each of the cut-out portions in the peripheral elongated region of the middle metal foil layer in the elongated, hermetic adhesion area has a predetermined width-wise depth as viewed and measured in a direction of the width of the peripheral elongated region of the middle metal foil layer from a peripheral edge of a pouchy casing, and wherein portions of the peripheral elongated region of said middle foil layer that are not cut out remain in the elongated hermetic adhesion area and the width of each of the remaining non-cut-out portions of the metal foil layer is at least ten times the thickness of the inner thermoplastic resin layer (1) in the elongated, hermetic adhesion area; and
(ii) the surface of the peripheral edge of the pouchy casing comprised of the laminate is provided with electric insulation at least at portions thereof around the terminal-withdrawal sites.
By virtue of the above-mentioned unique structure, the non-aqueous battery of the present invention having a thin configuration is advantageous not only in that it is light in weight, thin and flexible, but also in that it has an excellent moisture resistance and an excellent air tightness and is free from the danger of the occurrence of a short-circuiting at portions around the terminal-withdrawal sites. Therefore, the non-aqueous battery of the present invention can be advantageously used especially as a small, light-weight battery (for example, as a battery for portable equipments) having a high capacity and excellent safety.
In accordance with the tendency of reduction in potential of lithium. Conventionally, as casings for such batteries, metallic containers prepared by shaping a metal sheet into the form of a cylinder, a polygon, a coin or the like in accordance with the use of the battery have been used. However, it is difficult to reduce the weight of such a battery having a metallic casing, and also there are limitations with respect to the freedom of designing the shapes of metallic casings.
On the other hand, as compared to the above battery having a metallic casing, not only does a battery having a casing prepared from a laminate comprised mainly of a metal foil and a resin film become light in weight and flexible, but also the thickness of the battery can be easily reduced. In addition, with respect to such a battery having a casing made of a laminate comprised mainly of a metallic foil and a resin film, the sealing of the battery can be performed with ease during the production thereof. As examples of such batteries having laminate type casings, Unexamined Japanese Patent Application Laid-Open Specification Nos. 60-100362 and 1-112652 disclose non-aqueous primary batteries having laminate type casings, and Unexamined Japanese Patent Application Laid-Open Specification No. 60-49568 and British Patent Application Publication No. 2149197 disclose solid electrolyte batteries having laminate type casings. Each of the batteries disclosed in these prior art documents has a casing made of either a two-layer laminate comprised of a metal foil layer and a thermoplastic resin layer or a three-layer laminate comprised of an electrically insulating material layer, a metal foil layer and a thermoplastic resin layer. In such batteries, an electrochemical cell having terminals made of a SUS film or the like is enveloped by a pouchy casing prepared by a method in which the above-mentioned laminate is folded so as for the thermoplastic resin layers to be opposite to each other as inner layers, and the opposite inner thermoplastic resin layers are melt-adhered to each other along a periphery of the opposite inner thermoplastic resin layers to form a hermetic adhesion area, thereby hermetically sealing the pouchy casing, while positioning the terminals so that the terminals of the battery extend through and protrude from the hermetic adhesion area toward the outside of the pouchy casing.
In the conventional battery casings of a laminate type, the metal foil layer of the laminate serves to make the battery impervious to permeation of water vapor, and the electrically insulating material layer has an effect to protect the metal foil layer. The metal foil layer of the laminate used for the battery casing is made of aluminum or the like; the thermoplastic resin layer of the laminate is made of an ionomer, polyethylene, polypropylene or the like; and the electrically insulating material layer is made of polypropylene, polyethylene terephthalate or the like. Conventionally, the use of such a laminate for a battery casing has posed the following problems. A short-circuiting frequently occurs between the metal foil layer and the terminals during the melt-adhesion conducted for sealing the casing in the production of the battery. Further, after the production of the battery, a short-circuiting frequently occurs between the terminals and the metal foil layer exposed in the peripheral edge of the casing. The occurrence of these short-circuitings are serious problems from the viewpoint of reliability and safety during the production and use of the battery.
As a method for preventing the occurrence of a short-circuiting during the melt-adhesion for sealing the casing in the production of the battery, Unexamined Japanese Patent Application Laid-Open Specification No. 60-86754 and Examined Japanese Patent Application Publication No. 4-58146 disclose a method in which an intermediate electrically insulating material layer capable of remaining intact during the melt-adhesion is interposed between the metal foil layer and the thermoplastic resin layer of the laminate. However, batteries produced by this method do not solve the problem that a short-circuiting is likely to occur between the terminals and the metal foil layer exposed in the peripheral edge of the casing. Moreover, this method is also disadvantageous in that, since the intermediate electrically insulating material layer employed in this method is intact during the melt-adhesion for sealing the casing, a good adhesion cannot be obtained between the thermoplastic resin layer and the intermediate electrically insulating material layer, which results in a lowering of the air tightness and moisture resistance of the battery. Further, in this method, the production process becomes complicated.
There has been known a battery having a hermetically sealed pouchy casing made of a laminate of an inner thermoplastic structural adhesive layer, a middle metal foil layer and an outer high heat resistant polyester layer, in which the hermetic adhesion area is free of the metal foil layer, and the terminals extend through the elongated hermetic adhesion area (see Unexamined Japanese Patent Application Laid-Open Specification No. 3-62447 corresponding to European Patent Application Publication No. 397 248). In this battery, the casing has a portion along the inner side of the hermetic adhesion area, which portion has neither the hermetic adhesion area nor the metal foil layer. Therefore, when such battery is used, for example, as a secondary battery which is required to be capable of stable operation for a long period of time, problems arise that the battery suffers an intrusion of substances (such as water vapor) which impair battery performance, and also suffers a leaking-out of the solvent molecules of the electrolytic liquid.
Further, Unexamined Japanese Patent Application Laid-Open Specification No. 60-49568 discloses a method in which a battery is covered with a thermosetting resin, followed by a heat-curing of the thermosetting resin. This method is effective for preventing a short-circuiting between the metal foil layer and the terminals, but the elevated temperature necessary for curing the thermosetting resin is likely to adversely affect the electrochemical cell of the battery.
In this situation, the present inventors have made extensive and intensive studies with a view toward solving the above difficult problems accompanying the prior art, that is, toward developing a non-aqueous battery of a thin configuration, which comprises a non-aqueous electrochemical cell enveloped by a pouchy casing made by melt-adhering opposite sheets of laminates and which has advantages not only in that a short-circuiting between a metal foil layer and terminals can be surely prevented, but also in that the battery can be easily produced and exhibits an excellent air tightness and an excellent moisture resistance. As a result, it has unexpectedly been found that the above objective can be attained by a non-aqueous battery which employs a pouchy casing made of opposites sheets of at least-three-layer laminates, each comprising an inner thermoplastic resin layer, a middle metal foil layer and an outer electrically insulating material layer, wherein the pouchy casing has an elongated, hermetic adhesion area along a periphery of the pouchy casing in which adhesion area the opposite inner thermoplastic resin layers are melt-adhered to each other and the pouchy casing has terminal-withdrawal sites in the elongated, hermetic adhesion area, and wherein the pouchy casing satisfies at least one of the following characteristics (i) and (ii):
(i) the peripheral elongated region of the middle metal foil layer (2) has cut-out portions around the terminal-withdrawal sites in the elongated hermetic adhesion area of the pouchy casing through which the terminals extend wherein each of the cut-out portions in the peripheral elongated region of the middle metal foil layer in the elongated, hermetic adhesion area has a predetermined width-wise depth as viewed and measured in a direction of the width of the peripheral elongated region of the middle metal foil layer from a peripheral edge of a pouchy casing, and wherein portions of the peripheral elongated region of the middle metal foil layer that are not cut out remain in the elongated hermetic adhesion area and the width of each of the remaining non-cut-out portions of the metal foil layer is at least ten times the thickness of the inner thermoplastic resin layer (1) in the elongated, hermetic adhesion area; and
(ii) the surface of the peripheral edge of the pouchy casing comprised of the laminate is provided with electric insulation at least at portions thereof around the terminal-withdrawal sites.
That is, it has been found that, by the use of the above pouchy casing in a non-aqueous battery, not only can the occurrence of a short-circuiting be very greatly suppressed, but also the electrochemical cell can be easily sealed inside the casing while achieving an excellent air tightness and an excellent moisture resistance. The present invention has been made, based on this novel finding.
Therefore, a primary object of the present invention is to provide a non-aqueous battery of a lightweight and a thin configuration, which is free from the danger of the occurrence of a short-circuiting and exhibits an excellent air tightness, a high reliability and a high safety.
The foregoing and other objects, features and advantages of the present invention will be apparent from the following detailed description taken in connection with the accompanying drawings and the appended claims.